Optical data storage media (“optical media”) are media in which data is stored in an optically readable manner. Optical data media are used to distribute, store and access software and large volumes of data. Data is stored on optical media by forming optical deformations or marks at discrete locations in one or more layers of the medium. Such deformations or marks cause changes in light reflectivity. To read the data on an optical medium, an optical medium player or reader is used. An optical medium player or reader conventionally shines a small spot of laser light, the “readout” spot, through the disc substrate onto the data layer containing such optical deformations or marks as the medium or laser head rotates.
Original optical media, such as compact discs (CDs), are produced by stamping plastic blanks with a master mold piece, which is produced using costly, specialized equipment. Because of the high cost of optical media recording equipment, optical media recordings were considered, until recently, to be relatively secure against unauthorized copying. This situation has changed recently, as inexpensive optical media recording devices and read/write media have become available to consumers. A pirate can easily make unauthorized copies of optical media using a conventional personal computer with a read/write optical media drive, or with one read drive and one write drive, to make exact, digital copies of all types of optical media. The pirate extracts data byte-by-byte from one optical media, typically a legitimately-purchased original optical media, using a computer, and then writes the data to a blank writable or recordable optical media so as to make a pirate copy. As consumer demand for optical media remains high, and because such medium is easily reproduced at a low cost, counterfeiting has become prevalent. Resulting financial losses to the recording and software industries due to such pirate copying are estimated to be in the billions of dollars.
Many copy protection techniques and devices have been proposed in the art to limit the unauthorized copying of optical media. Currently, two general types of copy protection are used to protect against illegal copying of optical media, such as CD-ROMs (CD-read-only memory). The first type of copy protection includes software based, active methods of copy protection, which use ‘bad’ data written in a subchannel on the optical media to inhibit copying. Safedisc® is an example of a commercially available software program for CD authentication available from Macrovision Corporation of Santa Clara, Calif. The software does not work if it cannot find the expected bad data on the optical media, which indicates that the optical media is an original version. The ‘bad’ data is hard to copy, as only a few programs are capable of copying it, notably CLONECD and BLINDWRITE suite, which are available for download but not in stores.
The second type of copy protection currently in use includes passive methods of copy protection that writes sections of ‘bad’ data to the optical media to cause all of the data on the optical media to be uncopiable for many programs and devices, without an active step of checking for the ‘bad’ data. The bad sectors on the optical media, or the fact that more data was written to the optical media than it can physically hold according to the agreed-upon standard, causes the data to be uncopiable. Writing data in nonstandard formats to the optical media can cause the optical media to be rejected on certain drives. For example, certain drives have strict implementations of the CD-ROM standards (red book-audio CD, orange book-CD-R/W, yellow book-CD-ROM ISO9660, etc), and reject media (CDs) that do not strictly conform to the standard that is applicable to the data that it contains.
The prior methods of copy protection have several drawbacks. For example, the software based methods are available only on windows, as they are built on top of the Advanced SCSI (Small Computer Systems Interface) Programming Interface (ASPI) layer which provides a single interface into the many types of underlying optical media drives. UNIX/Linux does not have an ASPI layer equivalent. Therefore, copy protection software written for UNIX/Linux platforms requires separate functions for each and every optical media drive manufacturer and even model, making the copy protection software much harder to write and maintain. In addition, the software-based copy protection methods can be defeated by ‘unwrapping’ the executable so that it no longer checks for the bad sectors, as is the case for Safedisc, or by editing the binary executable, which is a non-trivial task. Once this is done, the program can be copied normally and the bad data is no longer needed. These methods can also be defeated simply by copying the CD-ROM onto a CD-R or CD-RW disc using software such as BLINDWRITE suite or CLONECD.